You can use script command. Build a line in .login or .profile of the user whose ssh session you want to monitor. When he logs in a script / log is generated of his I/O which gives you commands run and the output of those commands. In real time you can just tail the script and watch what the user does in real time.
Unable to paste a link for your referrance but you can just google on the command " script " and you will get the referrances.